A critical element for the design, characterization, and certification of materials and products produced by additive manufacturing processes is the ability to accurately and efficiently model the associated materials and processes. This is necessary for tailoring these processes to endow the associated products with proper geometrical and functional features. In an effort to address these needs in a computationally elegant and at the same time physically realistic manner, this paper presents the development of a methodology for simulating particle-based additive manufacturing processes which employs the Discrete Element Method (DEM). The details of the DEM-based methodology are presented first and the approach is demonstrated on a pair of test problems involving laser sintering of metal powders. The paper concludes with a discussion on how this approach may be generalized to broader classes of additive manufacturing systems, and details are given regarding future work which must be accomplished in order to further develop the present methodology.

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One crucial component of the additive manufacturing software toolchain is a class of geometric algorithms known as “slicers.” The purpose of the slicer is to compute a parametric toolpath defined at the mesoscale and associated g-code commands, which direct an additive manufacturing system to produce a physical realization of a three-dimensional input model. Existing slicing algorithms operate by application of geometric transformations upon the input geometry in order to produce the toolpath. In this paper we introduce an implicit slicing algorithm that computes mesoscale toolpaths from the level sets of heuristics-based or physics-based fields defined over the input geometry. This enables computationally efficient slicing of arbitrarily complex geometries in a straight forward fashion. The calculation of component “infill” is explored, as a process control parameter, due to its strong influence on the produced component’s functional performance. Several examples of the application of the proposed implicit slicer are presented. It is demonstrated — via proper experimentation — that the implicit slicer can produce a mesoscale structure leading to objects of superior functional performance such as greatly increased stiffness and ultimate strength without an increase of mass. We conclude with remarks regarding the strengths of the implicit approach relative to existing explicit approaches, and discuss future work required in order to extend the methodology.

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In this paper, we explore the topic of Fused Filament Fabrication (FFF) 3D-printing. This is a low-cost additive manufacturing technology which is typically embodied in consumer-grade desktop 3D printers capable of producing useful parts, structures, and mechanical assemblies. The primary goal of our investigation is to produce an understanding of this process which can be employed to produce high-quality, functional engineered parts and prototypes. By developing this understanding, we create a resource which may be turned to by both researchers in the field of manufacturing science, and industrial professionals who are either considering the use of FFF-enabled technologies such as 3D printing, or those who have already entered production and are optimizing their fabrication process. In order to paint a cohesive picture for these readers, we examine several topic areas. We begin with an overview of the FFF process, its key hardware and software components, and the interrelationships between these components and the designer. With this basis, we then proceed to outline a set of design principles which facilitate the production of high quality printed parts, and discuss the selection of appropriate materials. Following naturally from this, we turn to the question of feedstock materials for FFF, and give advice for their selection and use. We then turn to the subject of the as-printed properties of FFF parts and the strong non-isotropic response that they exhibit. We discuss the root causes of this behavior and means by which its deleterious effects may be mitigated. We conclude by discussing a mixed numerical/experimental technique which we believe will enable the accurate characterization of FFF parts and structures, and greatly enhance the utility of this additive manufacturing technology. By formalizing and discussing these topics, we hope to motivate and enable the serious use of low-cost FFF 3D printing for both research and industrial applications.

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Thin film crystallites typically exhibit normal or abnormal growth with maximum grain size limited by energetic and geometric constraints. Although epitaxial methods have been used to produce large single crystal regions, they impose limitations that preclude some compelling applications. The generation of giant grain thin film materials has broad implications for fundamental property analysis and applications. This work details the production of giant grains in Ag films (2.5 μm-thick), ranging in size from ≈50 μm to 1 mm, on silicon nitride films upon silicon substrates. The presence of oxygen during film deposition plays a critical role in controlling grain size and orientation.